FILE - In this Tuesday, April 21, 2015, file photo, U.S. Navy's amphibious assault vehicles with Philippine and U.S. troops on board maneuver in the waters during a combined assault exercise facing the contested Scarborough Shoal in waters off of the Philippines. The Chinese government, Saturday, Jan 20, 2018, accused the U.S. of trespassing in its territorial waters when a U.S. guided missile destroyer sailed near the disputed Scarborough Shoal in the South China Sea. (AP Photo/Bullit Marquez, File)